Acid phosphatase localization in endocytosed horizontal cell gap junctions

Gap junction (GJ) endocytosis appears to be part of a cycle of GJ renewal in horizontal cells of the teleost fish retina. At least three stages of GJ endocytosis in these neurons have been identified using conventional electron microscopy (EM): invagination of GJ membranes (GJ blebs); free GJ vesicl...

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Bibliographic Details
Published in:Visual neuroscience 1992-01, Vol.8 (1), p.77-81
Main Authors: Vaughan, Dana K., Lasater, Eric M.
Format: Article
Language:English
Subjects:
Acid phosphatase
Acid Phosphatase - metabolism
Animals
Bass
Degradation
Endocytosis
Gap junction
Golgi Apparatus - enzymology
Golgi Apparatus - ultrastructure
Histocytochemistry
Horizontal cell
Intercellular Junctions - enzymology
Intercellular Junctions - ultrastructure
Lysosome
Lysosomes - enzymology
Lysosomes - ultrastructure
Neuron
Neurons - enzymology
Neurons - ultrastructure
Retina
Retina - enzymology
Retina - ultrastructure
Short Communication
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Summary:Gap junction (GJ) endocytosis appears to be part of a cycle of GJ renewal in horizontal cells of the teleost fish retina. At least three stages of GJ endocytosis in these neurons have been identified using conventional electron microscopy (EM): invagination of GJ membranes (GJ blebs); free GJ vesicles; and GJ vesicle fusion with mature lysosomes (Vaughan & Lasater, 1990a). In the present study, EM-level acid phosphatase (AP) histochemistry of white bass retina was used to determine at what stage enzymatic degradation of endocytosed GJs begins. Electron-dense AP reaction product was observed within the trans face of the Golgi apparatus, mature lysosomes, and occasional, internal GJ vesicles. In contrast, GJ blebs, peripheral GJ vesicles, and most internal GJ vesicles lacked AP reaction product. These results support the idea that at least some of the GJ vesicles observed within these retinal neurons arise from endocytosis, are on a degradative pathway, and can be termed GJ “endosomes.” Furthermore, GJ vesicles appear to be initially free of AP, but some later acquire it (presumably from transport vesicles bearing degradative enzymes). It is still unclear whether our previous report of GJ vesicle fusion with mature lysosomes is a subsequent step in GJ degradation or part of a different degradative pathway altogether.
ISSN:0952-5238
1469-8714
DOI:10.1017/S0952523800006519